Jillian has $50 that she plans on investing in an account that will double her money every week. This can be represented by the equation M = 50(2)x where M represents the amount of money she has and x represents the number of weeks that have passed. Her uncle Charlie gives her a gift of $400 so she decides to start her investement with that money plus the $50 she already had. What should be changed in the equation M = 50(2)x to represent the new situation?